CN105093379A - Micro retardation film - Google Patents

Abstract

The invention provides a micro phase difference film. The micro phase difference film includes: a microstructure layer is arranged on a base material and is provided with a plurality of trapezoidal micro-protrusions, and the included angle of the bottoms of the trapezoidal micro-protrusions is 12-85 degrees; and sequentially arranging a conformal optical alignment layer and a liquid crystal phase difference layer on the microstructure layer. The micro phase difference film can solve the problem that bright lines are generated due to light leakage at the junction of two different phases, thereby improving the quality of 3D display.

Description

Micro retardation film

technical field

The present invention relates to an optical film, and in particular to a micro retardation film.

Background technique

Micro-retarder film (Patterned Retarder, Micro Retarder) is a micro-structured optical film with even-numbered column regions and odd-numbered column regions on the film surface. The phase difference value (phasedifference) between the odd and even column regions in the aforementioned micro-retardation film is usually λ/2, for example, the phase (phase) of the odd and even column regions can be 0 and λ/2 or λ/4 and -λ/ 4 and so on. Therefore, when the micro-retardation film is attached to the outer layer of the display, it can convert the light polarization states of the pixels in the odd and even columns of the display to present 3D images.

The earliest micro-retardation film manufacturing method is a mechanical processing method. First, a layer of retardation layer is formed, and then the retardation layer in the odd-numbered or even-numbered column area is removed by a knife die, so that the phase difference between the odd-numbered and even-numbered columns The value is λ/2.

The liquid crystal ISO phase production method is to first coat the liquid crystal on the entire substrate, and then expose the odd-numbered or even-numbered columns to make the phase value of the odd-numbered or even-numbered columns λ/2. Then, heat the uncured liquid crystal to become an ISO phase, and then perform thermal curing to make it have no phase difference (that is, its phase value is 0).

The dual-area alignment method (using rubbing or photo-alignment technology) is to allow the odd-numbered or even-numbered areas to have different alignment directions, so that the phase difference between the odd-numbered and even-numbered areas is λ/2.

In the above-mentioned various methods, at the junction of two different phases, there may be a problem of liquid crystal alignment disorder, resulting in light leakage and the formation of bright lines, resulting in a decrease in the display quality of 3D images.

Contents of the invention

Therefore, one aspect of the present invention is to provide a micro-retardation film to solve the above-mentioned problem of light leakage at the junction of two different phases, resulting in bright lines, and improve the quality of 3D display.

The micro-retardation film of the present invention comprises from bottom to top: a substrate, a microstructure layer, an optical alignment layer, and a liquid crystal retardation layer. The above-mentioned microstructure layer is configured on the base material, and the microstructure layer has a plurality of trapezoidal micro-protrusions, and the included angle at the bottom of the trapezoidal micro-protrusions is 12-85 degrees. The above optical alignment layer is configured conformally on the microstructure layer, and the liquid crystal retardation layer is configured on the optical alignment layer.

According to an embodiment of the present invention, the included angle at the bottom of the trapezoidal micro-protrusions is 12-65 degrees.

According to another embodiment of the present invention, the height of the trapezoidal micro-protrusions is 0.5-2.0 μm.

According to yet another embodiment of the present invention, the width of the bottom surface and the top surface of the trapezoidal micro-protrusions is 100-1000 μm.

According to yet another embodiment of the present invention, the material of the microstructure layer is ultraviolet curable resin or thermal curable resin, such as acrylic resin, silicone resin or polyurethane.

According to yet another embodiment of the present invention, the material of the substrate may be, for example, polyethylene terephthalate, polycarbonate, cellulose triacetate, polymethyl methacrylate or cycloolefin polymer.

According to still another embodiment of the present invention, the material of the photo-alignment layer can be photo-induced cross-linking resin (photo-induced cross-linking resin), photo-induced isomerization resin (photo-induced isomerization resin) or photo-cleavage resin (photo -induceddecompositionresin), which has a photopolymerizable functional group, such as a cinnamate group, a coumarin ester group, a phenyl styryl ketone group, a maleimide group, a quinolinone group or a bisphenylene group methyl.

According to yet another embodiment of the present invention, the thickness of the photo-alignment layer is 50-100 nm.

The advantage of the present invention is that the micro-retardation film of the present invention can solve the problem of light leakage at the junction of two different phases of the prior art micro-retardation film so as to produce bright lines.

The above summary is intended to provide a simplified summary of the disclosure to provide readers with a basic understanding of the disclosure. This summary is not an extensive overview of the disclosure and it is not intended to identify key/critical elements of the embodiments of the invention or to delineate the scope of the invention. After referring to the following embodiments, those with ordinary knowledge in the technical field of the present invention can easily understand the basic spirit and other invention objectives of the present invention, as well as the technical means and implementation aspects adopted by the present invention.

Description of drawings

In order to make the following and other objects, features, advantages and embodiments of the present invention more comprehensible, the accompanying drawings are described as follows:

FIG. 1A is a schematic top view illustrating a micro-retardation film according to an embodiment of the present invention;

Fig. 1B is a schematic diagram of a cross-sectional structure showing the section line B-B' in Fig. 1A;

FIG. 2 is a flow chart illustrating the manufacture of a micro-retardation film according to an embodiment of the present invention;

Figure 3A shows that after the microstructure layer is stripped, there is residual glue at the junction of the bottom surface and the slope of the microstructure layer;

Fig. 3B-Fig. 9 are the photographs showing each experimental example and comparative example observed with a polarizing microscope;

Among them, the symbol description:

100: micro-retardation film 100a: first phase region

100b: second phase area 100c: junction area

110: substrate 120: microstructure layer

122: trapezoidal micro-protrusion 124: top surface

126: bottom surface 128: slope

130: photo-alignment layer 134: top surface

136: Bottom surface 138: Inclined surface

140: liquid crystal phase difference layer 300: residual glue

h: height of trapezoidal microprojection

θ: Angle between the slope of the trapezoidal micro-protrusion and the extension line of the bottom surface.

Detailed ways

According to the above, a micro-retardation film is provided, which can solve the above-mentioned problem that the micro-retardation film has light leakage at the junction of two different phases, resulting in bright lines. In the following description, an exemplary structure of the aforementioned micro-retardation film and an exemplary manufacturing method thereof will be introduced. For the sake of easy understanding of the described embodiments, a number of technical details will be provided below. Of course, not all embodiments require these technical details. Meanwhile, some well-known structures or elements are only drawn schematically in the drawings to appropriately simplify the contents of the drawings.

Structure of Microretardation Film

Please refer to FIG. 1A-FIG. 1B at the same time. FIG. 1A is a schematic top view of a micro-retardation film according to an embodiment of the present invention, and FIG. 1B is a schematic cross-sectional structure diagram showing the section line B-B' in FIG. 1A.

In FIG. 1A , the micro-retardation film 100 has a first phase region 100a, a second phase region 100b and a junction region 100c, wherein the phase difference between the first phase region 100a and the second phase region 100b is λ/2. In the schematic cross-sectional structure of FIG. 1B , the microretardation film 100 has a substrate 110 , a microstructure layer 120 , a conformal (conformal) photo-alignment layer 130 and a liquid crystal retardation layer 140 .

The material of the above-mentioned substrate 110 can be, for example, polyethylene terephthalate (polyethyleneterephthalate, PET), polycarbonate (polycarbonate, PC), triacetylcellulose (triacetylcellulose, TAC), polymethyl methacrylate ( polymethylmethacrylate, PMMA) or cyclo-olefin polymer (cyclo-olefin polymer, COP). The smaller the phase difference value of the base material 110, the better, so as not to affect the display effect of the final 3D image. For example, the phase difference of the substrate 110 may be less than 20 nm, preferably 0 nm. The thickness of the substrate is about 25–200 μm.

The aforementioned microstructure layer 120 has a plurality of trapezoidal micro-protrusions 122 . The top surface 124 , the bottom surface 126 and the inclined surface 128 of the trapezoidal micro-protrusion 122 respectively correspond to the first phase region 100 a , the second phase region 100 b and the junction region 100 c of the micro-retardation film 100 , as shown in FIG. 1B . The height h of the trapezoidal micro-protrusions 122 is mainly determined by the birefringence of the liquid crystal material of the liquid crystal retardation layer 140 . The greater the birefringence difference (Δn) of the liquid crystal material of the liquid crystal phase difference layer 140, the smaller the required height h, so that the phase difference between the first phase region 100a and the second phase region 100b is λ/2 . Generally, the height h of the trapezoidal micro-protrusions 122 is about 0.5-2.0 μm, for example, 2 μm. The width of the top surface 124 and the bottom surface 126 of the trapezoidal micro-protrusion 125 is about 100-1000 μm, for example, 500 μm. The included angle θ between the slope 128 of the microstructure layer 120 and the extension line of the bottom surface 126 (that is, the included angle θ at the bottom of the trapezoidal micro-protrusions 122 ) is preferably 12-85 degrees, more preferably 12-65 degrees.

The material of the microstructure layer 120 is cured curable resin, which includes UV curable resin and thermo-curable resin. For example, the above-mentioned curable resin can be acrylic resin, silicone resin or thermosetting polyurethane resin. The above-mentioned acrylic resin may be, for example, methacrylate resin, the above-mentioned silicone resin may be, for example, polydimethylsiloxane, and the above-mentioned thermosetting polyurethane resin may be, for example, polyurethane.

The above-mentioned photo-alignment layer 130 is conformal to the surface of the microstructure layer 120, so it also has structures such as a top surface 134, a bottom surface 136, and an inclined surface 138, which correspond to the first phase region 100a, The second phase region 100b and the junction region 100c are shown in FIG. 1B . The thickness of the photo-alignment layer 130 is about 50-100 nm.

The material of the photo-alignment layer 130 is photo-cured photo-alignment resin. Photo-alignment resin is a kind of light-sensitive material, which can be irradiated with linear polarized ultraviolet light in a specific direction to trigger various anisotropic photo-reactions, and then induce the liquid crystal molecules on it to align in an orderly manner. The photo-alignment resin mentioned above belongs to photo-induced cross-linking resin (photo-induced cross-linking resin), which contains various functional groups capable of photopolymerization, such as cinnamate (cinnamate), coumarin ester ( coumarin), phenyl styrene ketone (chalcone), maleimide (maleimide), quinolinone (quinolinone) or bis(benzylidene)]. The photo-alignment resins with the above-mentioned functional groups require lower exposure energy, and only need 5mJ/cm ² at the minimum to produce an alignment effect.

The above-mentioned liquid crystal retardation layer 140, since its upper surface is flat, but the surface of the photo-alignment layer 130 below it is uneven, so the liquid crystal retardation layer 140 has different thicknesses, causing the incident polarized light to pass through with After the liquid crystal phase difference layer 140 with different thicknesses, the vibration direction of the electromagnetic field of light will be rotated to different angles. Therefore, the light passing through regions of different thicknesses of the liquid crystal retardation layer 140 will have different phases, so that the display can display 3D images.

The liquid crystal material used in the liquid crystal retardation layer 140 is a polymerizable liquid crystal material, including a liquid crystal material that can be cured by light or by heat. Since the thickness difference between the thickness of the liquid crystal phase difference layer 140 in the first phase region 100a and the second phase region 100b is the height h of the trapezoidal micro-protrusion 122, and the first phase region 100a and the second phase region 100b The phase difference value is λ/2. Therefore, the birefringence difference Δn of the liquid crystal material and the thickness difference between the first phase region 100 a and the second phase region 100 b of the liquid crystal retardation layer 140 must comply with the relational expression λ/2=Δn×h.

For example, when the wavelength of the incident light is 560nm and the birefringence difference of the liquid crystal material is 0.14, the thickness of the liquid crystal retardation layer 140 in the first phase region 100a is 1 μm, and the thickness in the second phase region 100b is 3 μm. . As another example, when the wavelength of the incident light is 560 nm and the birefringence difference of the liquid crystal material is 0.56, the thickness of the liquid crystal retardation layer 140 in the first phase region 100a is 0.5 μm, and the thickness of the second phase region 100b is 0.5 μm. The thickness is 1.5 μm.

Manufacturing method of micro-retardation film

Please refer to FIG. 2 for the manufacturing method of the aforementioned micro-retardation film, which is a flowchart illustrating a manufacturing process of a micro-retardation film according to an embodiment of the present invention. For the following detailed description, please refer to FIG. 1A-FIG. 1B and FIG. 2 at the same time.

First, in step 200, a layer of curable resin is coated on the substrate 110, and the coating method can be any available method, such as slit coating (diecoating) or gravure coating (gravurecoating). ). Next, the above-mentioned curable resin layer is embossed with a mold roller or a mold stamp with a three-dimensional pattern, so that trapezoidal micro-protrusions 122 are formed on the surface of the curable resin layer. In step 220 , the curable resin is cured by using light or heat according to the material of the curable resin. Then in step 230 , the cured resin layer is stripped to form the microstructure layer 120 . The materials of the base material 110 and the curable resin have been described in detail above, and thus will not be repeated here.

In step 240, a layer of photo-alignment resin is conformally coated on the microstructure layer 120, and the coating method can be any available method, such as spin coating method. Then in step 250 , the photo-alignment resin is cured with linear polarized light to form the photo-alignment layer 130 . The angle between the polarization direction of the above-mentioned linearly polarized light and the direction of each phase region of the micro-retardation film 100 (that is, the first phase region 100a, the second phase region 100b, and the junction region 100c) is not 0 or 180 degrees, that is, linear The angle between the polarization direction of the polarized light and the direction of the phase regions of the micro-retardation film 100 (hereinafter referred to as the alignment angle) is non-parallel. In addition, since the microstructure layer 120 connects the top surface 124 and the bottom surface 126 with the inclined surface 128 instead of connecting the top surface 124 and the bottom surface 126 with the vertical surface, it is easier to coat the photo-alignment resin on the inclined surface 128. It is easier to cure when exposed to polarized light.

In step 260, a liquid crystal layer is coated on the photo-alignment layer 130, and the coating method can be any available method, such as spin coating method. Then in step 270 , the liquid crystal layer is cured by light or heat to form the liquid crystal retardation layer 140 , and the fabrication of the micro retardation film 100 is completed. Similarly, since the photo-alignment layer 130 connects the top surface 134 and the bottom surface 136 with the inclined surface 138 instead of connecting the top surface 134 and the bottom surface 136 with the vertical surface, it is easier to coat the liquid crystal layer on the inclined surface 138. It is easier to cure by exposure to light.

Example

The manufacturing methods of the micro-retardation films of the following experimental examples and comparative examples are as follows. The only difference is that the angle θ at the bottom of the trapezoidal micro-protrusions 122 in FIG. 1B is different.

First, a layer of acrylic resin curable by ultraviolet light is coated on a triacetylcellulose (TAC) substrate. After imprinting with a mold, the resin layer is irradiated with ultraviolet light, and after the resin layer is cured and shaped, the film is removed to form a microstructure layer.

Next, let methyl ethyl ketone (methylethylketone) and cyclopentanone (cyclopentanone) be prepared into a mixed solvent at a weight ratio of 1:1. Then a photo-alignment resin (Rolic, Switzerland, model ROP103, cinnamate, solid content 10%) was added to the mixed solvent to prepare a photo-alignment resin solution with a solid content of 1.25 wt%. Next, the photo-alignment resin solution was conformally coated on the microstructure layer by spin coating (3000 rpm, 40 seconds), and then dried (100° C., 2 minutes) to remove the solvent. Finally, the dried photo-alignment film was irradiated with linearly polarized extreme ultraviolet light (alignment angle: 45°, irradiation dose: 180 mJ/cm ² ), so that the photo-alignment film was cured.

Next, the liquid crystal powder was dissolved in cyclopentanone to prepare a liquid crystal solution with a solid content of 20 wt%. The liquid crystal solution was coated on the photo-alignment layer by spin coating (1000 rpm, 20 seconds), and then dried (60° C., 5 minutes) to remove the solvent. Finally, under nitrogen, irradiate the liquid crystal layer with ultraviolet light (irradiation dose: 120mJ/cm ² ), let it solidify, form a liquid crystal phase difference layer, and complete the micro phase difference film.

The test results of the 3D display screens of the experimental examples and comparative examples are shown in Table 1 below and FIGS. 3A-9 . In the photographs of FIG. 3B, FIG. 4, FIG. 5B, and FIG. 9, the polarization direction of the light source of the polarizing microscope is parallel or perpendicular to the alignment angle of the sample. Therefore, under normal conditions, if there is no light leakage problem, the observed display screen will be completely black. If there is a problem of light leakage in the boundary region, bright lines will be generated in the boundary region between the first phase region and the second phase region. Among them, if the aforementioned observation conditions are used in FIG. 9 , defects cannot be observed. Therefore, in order to highlight the problem of light leakage, the polarizing microscope uses a stronger light source to highlight the problem of light leakage.

In FIG. 5A , FIG. 6 , FIG. 7 , and FIG. 8 , the included angles between the polarization direction of the light source of the polarizing microscope and the sample alignment angle are other angles. In addition, in order to highlight the phase difference of the micro-retardation film under a polarizing microscope, a layer of 1/4 wave plate is added to the micro-retardation film, so that an image in which a bright area and a dark area are alternately arranged can be observed.

Table 1: The influence of the bottom angle of the trapezoidal micro-protrusions of each experimental example and comparative example on the 3D display screen

From the results of Table 1 and Fig. 3A-Fig. 9, it can be seen that when the bottom angle of the trapezoidal micro-protrusions in the microstructure layer is too large (87.1° as in Comparative Example 1), it is easier for the bottom surface of the microstructure layer and the slope junction. The problem of residual glue (please see the residual glue 300 in FIG. 3A ) is generated, and the arrangement of the liquid crystal molecules on the place is disordered, so that the interface area of the micro-retardation film produces bright lines (please see FIG. 3B ), And the pixels will also have the problem of light leakage.

When the bottom angle of the trapezoidal micro-protrusions in the microstructure layer is slightly reduced (84.3° as in Experimental Example 1), the problem of residual glue at the junction of the bottom surface of the microstructure layer and the slope can be reduced, and the problem of pixel light leakage can also be solved. (See Figure 4).

However, the included angle at the bottom of the trapezoidal micro-protrusions in Experimental Example 2-5 is 12.5°-63.4°. Not only did the trapezoidal micro-protrusions not leave any residual glue after the film was removed, but also the junction area of the micro-retardation film would not produce bright lines. The pixels also do not suffer from light leakage (see Figures 5A-8).

However, when the angle between the bottom of the trapezoidal micro-protrusions in the microstructure layer continues to decrease, although there will still be no problem of residual glue leading to the problem of bright lines in the junction area of the micro-retardation film, but due to the uneven phase, the pixels will start to have light leakage again. problem (see Figure 9), resulting in a decrease in display quality.

Therefore, it can be known from the above embodiments that the included angle at the bottom of the trapezoidal micro-protrusions in the microstructure layer should not be too large or too small. When it is about 12-85 degrees, normal 3D image display quality can be obtained.

Although the present invention has been disclosed above in terms of implementation, it is not intended to limit the present invention. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall prevail as defined by the appended claims.

Claims (10)

1. a micro-bit phase difference film, is characterized in that, this micro-bit phase difference film comprises:

One base material;

One microstructured layers, is configured on described base material, and described microstructured layers has multiple trapezoidal micro-protuberance, and the bottom angle of described trapezoidal micro-protuberance is 12-85 degree;

One photo-alignment layer, is conformally configured on described microstructured layers; And

One liquid crystal phasic difference layer, is configured in described photo-alignment layer.

2. micro-bit phase difference film as claimed in claim 1, it is characterized in that, the bottom angle of wherein said trapezoidal micro-protuberance is 12-65 degree.

3. micro-bit phase difference film as claimed in claim 1, it is characterized in that, the height of wherein said trapezoidal micro-protuberance is 0.5 – 2.0 μm.

4. micro-bit phase difference film as claimed in claim 1, it is characterized in that, the bottom surface of wherein said trapezoidal micro-protuberance and the width of end face are 100 – 1000 μm.

5. micro-bit phase difference film as claimed in claim 1, it is characterized in that, the material of wherein said microstructured layers is ultraviolet curable resin or heat reactive resin.

6. micro-bit phase difference film as claimed in claim 1, it is characterized in that, the material of wherein said microstructured layers is acryl resin, silica resin or polyamine formic ether.

7. micro-bit phase difference film as claimed in claim 1, it is characterized in that, the material of wherein said base material is polyethylene terephthalate, polycarbonate, Triafol T, polymethylmethacrylate or cyclic olefin polymer.

8. micro-bit phase difference film as claimed in claim 1, it is characterized in that, the material of wherein said photo-alignment layer is photocrosslinking type resin.

9. micro-bit phase difference film as claimed in claim 8, it is characterized in that, wherein said photocrosslinking type resin has and can carry out photopolymerization reaction functional group, and described functional group is cinnamic acid ester group, cumarin ester group, styryl phenyl ketone group, dimaleoyl imino, quinoline ketone group or two benzylidene.

10. micro-bit phase difference film as claimed in claim 1, it is characterized in that, the thickness of wherein said photo-alignment layer is 50 – 100nm.